With the recent increase in capacity of recording media, there becomes widespread a system for distributing digitized contents (hereinafter, referred to simply as “contents”) obtained by digitizing copyrighted works such as movie and music, recording the digitized contents in recording media, and playing back the digitized contents. In such a system, playback and copy of a content need to be performed only under authorization by an owner of a copyright of the content in order to protect the copyright of the content.
Also, in order to improve user's convenience in watching and acquiring contents under the above authorization, Patent Literature 1 discloses a system for allowing a user to watch a content, which the user has already purchased via his device, on another device without purchasing the content again via the other device.
According to the Patent Literature 1, content purchase information of a user is managed by a server device. Assume that a certain user purchases a content having a title name X via a device, and then he tries to again acquire the content having the title name X via another device, for example. In such a case, a user ID for identifying a user A is input into the other device, and is transmitted to the server device. If the server device checks that the certain user is identical with the user A by verifying whether the user ID has been authenticated, the server device distributes the content having the title name X also to the other device free of charge.